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Tsukuba, Japan

Yamashita T.,University of Tokyo | Yamashita T.,BEANS Laboratory | Itoh T.,Japan National Institute of Advanced Industrial Science and Technology | Suga T.,University of Tokyo
Journal of Japan Institute of Electronics Packaging

An anti-stiction coating with a self-assembled monolayer (SAM) was investigated for ohmic contact micro-electro-mechanical system (MEMS) switches with low-load contacts. SAMs of thiophenol (TP) or 2-naphthalenethiol (2-NT) were coated on Au samples with variations in surface roughness to investigate the effects of the surface asperities on the adhesion force. The adhesion force was measured using a silicon tipless cantilever in the relative humidity range of 10 to 85% for the SAM coated samples and compared with those for the Au and SiO2 sample surfaces. The adhesion force measurements indicate that the TP and 2-NT coatings can prevent a liquid meniscus from forming on the device surfaces due to their hydrophobic character caused by the protruding aromatic group. In addition, it was confirmed that these coatings could reduce van der Waals forces more than the Au coating. Based on these results, SAMs of TP and 2-NT have excellent potential as anti-stiction coatings for MEMS switch contacts. Source

Takamatsu S.,Tokyo University of Information Sciences | Takamatsu S.,BEANS Laboratory | Takahata T.,Tokyo University of Information Sciences | Matsumoto K.,Tokyo University of Information Sciences | Shimoyama I.,Tokyo University of Information Sciences
Journal of Micromechanics and Microengineering

We have developed a process to pattern the conductive polymer of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) film and the insulation polymer of the perfluoro polymer (Cytop) with a Parylene lift-off method for the purpose of fabricating a PEDOT:PSS-based electrochromic display device. Because conventional micro-patterning processes decrease the conductivity of organic electronic polymers due to the destructive solutions of photolithography, PEDOT:PSS and Cytop polymers were patterned by using the dry lift-off film of Parylene. Its patterning resolution of PEDOT:PSS was found to be as low as 20 μm. The insulation layer of Cytop was also patterned on the PEDOT:PSS pattern with the same resolution. This process was able to pattern the 300 μm wide wiring and 1 mm square pixels of PEDOT:PSS and the Cytop to cover the entire area except for the pixels constructed to form an electrochromic display. Finally, the fabricated 4 × 4 pixel device displayed a simple shape, a transverse line. © 2011 IOP Publishing Ltd. Source

Miwa K.,BEANS Laboratory | Nishimori Y.,BEANS Laboratory | Ueki S.,BEANS Laboratory | Sugiyama M.,University of Tokyo | And 2 more authors.
Journal of Vacuum Science and Technology B: Microelectronics and Nanometer Structures

A low-damage silicon etching technology for fabricating microelectromechanical system (MEMS) devices using a neutral beam is reported. Neutral beams were produced from Cl2 plasma in an etching apparatus and were used to etch silicon trenches and MEMS devices. Si trench etch rate depended on the bias voltage applied to an aperture, used to produce the neutral beam. Etch rate decreased with increasing Si trench aspect ratio. This trend was minimized by enlarging the aspect ratio of through-holes in the aperture. The silicon trench profile was influenced by the aspect ratio of through-holes in the aperture. Etched Si surfaces were smooth, and no damage/defects were observed by transmission electron microscopy. Si etching of MEMS devices with smooth surfaces and scallop free sidewalls was achieved. The mechanical characteristics of an oscillator etched with the neutral beam were superior to those of that etched using a conventional Bosch process. © 2013 American Vacuum Society. Source

Li Y.F.,BEANS Laboratory | Tomizawa Y.,BEANS Laboratory | Koga A.,Toshiba Corporation | Hashiguchi G.,University of Shizuoka | And 2 more authors.
Proceedings of the IEEE International Conference on Micro Electro Mechanical Systems (MEMS)

A novel trench-type anti-wear microprobe with nano-scale electric contacts was proposed as an AFM probe to overcome the problem of probe tip wear and improve patterning stability in Atomic force microscope (AFM) local anodic oxidation (LAO) lithography. The proposed microprobe was fabricated using MEMS technique. The patterning and wear properties of the fabricated microprobe in AFM LAO lithography were investigated in terms of the change in the drawn line width and probe tip shape before and after a 20 mm scan. SEM images of the probe tips before and after the scan indicated that there was no obvious damage in the fabricated probe tip while apparent damage could be found on the conventional type probe tip. AFM LAO lithography results showed that the fabricated microprobe maintained a stable pattering performance before and after the 20 mm scan while the conventional type probe was unable to draw due to tip wear after the scan. Source

Kano T.,Keio University | Suito E.,Keio University | Hishida K.,Keio University | Miki N.,Keio University | Miki N.,BEANS Laboratory
Japanese Journal of Applied Physics

In this study, we experimentally revealed that the microscale surface geometry of anodes strongly affects the performance of microbial fuel cells (MFCs). MFCs have much need to be improved in their power. The power generated by an MFC is considered to be strongly affected by the interaction between the organic bacteria and the inorganic electrode surfaces. In prior work, the nanoscale surface roughness of the anode was discussed; however, we consider that the microscale surface geometry may play a crucial role given the bacteria size of micrometer order. We used a two-chamber MFC and the direct electron transfer bacteria Shewanella putrefaciens. We prepared seven types of anode electrodes with different microscale surface geometries and experimentally found that the MFC performance depended on the contact area between the bacteria and the anode. The MFC generated the maximum power when the contact area between the anode and bacteria was the largest. © 2012 The Japan Society of Applied Physics. Source

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